Reverse bipolar junction transistor integrated circuit

ABSTRACT

A Reverse Bipolar Junction Transistor (RBJT) integrated circuit comprises a bipolar transistor and a parallel-connected distributed diode, where the base region is connected neither to the collector electrode nor to the emitter electrode. The bipolar transistor has unusually high emitter-to-base and emitter-to-collector reverse breakdown voltages. In the case of a PNP-type RBJT, an N base region extends into a P− epitaxial layer, and a plurality of P++ collector regions extend into the base region. Each collector region is annular, and rings a corresponding diode cathode region. Parts of the epitaxial layer serve as the emitter, and other parts serve as the diode anode. Insulation features separate metal of the collector electrode from the base region, and from P− type silicon of the epitaxial layer, so that the diode cathode is separated from the base region. This separation prevents base current leakage and reduces power dissipation during steady state on operation.

TECHNICAL FIELD

The described embodiments relate to integrated circuits that includeboth a bipolar transistor as well as a parallel-connected distributeddiode, to AC line filters and to rectifiers employing such integratedcircuits, and to related structures and methods.

BACKGROUND INFORMATION

There are four diodes in a conventional full-wave bridge rectifier. U.S.patent application Ser. No. 13/931,599 discloses a circuit referred tohere as a “low forward voltage rectifier” that can be used in place of adiode in such a full-wave bridge rectifier. The “low forward voltagerectifier” includes a “Reverse Bipolar Junction Transistor” (RBJT)integrated circuit. The RBJT integrated circuit includes a bipolartransistor and a parallel-connected distributed diode. The diode is“parallel” in the sense that forward current through the diode flows inthe same direction as the main current flow through the bipolartransistor when the transistor is on, as opposed to what is sometimescalled an “anti-parallel” diode. The term “low forward voltagerectifier” as it is used here in this patent document refers to one suchRBJT integrated circuit, and also may or may not include associatedinductive current splitting circuitry that controls the base current ofthe RBJT such that the bipolar transistor and its parallel-connecteddiode operate together as a low forward voltage rectifier. Where thereordinarily would be a larger forward voltage drop across a standarddiode (for example, about 1.0 volts) when current is flowing through thediode in a conventional full-wave bridge rectifier, a lower forwardvoltage drop (for example, 0.1 volts) is seen across each rectifier of afull-wave bridge rectifier that employs low forward voltage rectifiersrather than conventional diodes. This lower forward voltage droptranslates into higher energy efficiency, less heat generation in thefull-wave bridge rectifier, and less cost involved in providing anynecessary heat sinking. How an integrated circuit involving both abipolar transistor and a parallel-connected distributed diode can befabricated, and how an RBJT integrated circuit can be made to operate asa rectifier having a low forward voltage drop, are described in: 1) U.S.Pat. No. 8,648,399, filed on Nov. 17, 2011, by Kyoung Wook Seok, and 2)U.S. Patent Publication US20130285210, published Oct. 31, 2013, filed asU.S. patent application Ser. No. 13/931,599 on Jun. 28, 2013, by KyoungWook Seok (the entire subject matter of these two patent documents isincorporated herein by reference).

SUMMARY

A Reverse Bipolar Junction Transistor (RBJT) integrated circuitcomprises a bipolar transistor and a parallel-connected distributeddiode. The bipolar transistor has an unusually high emitter-to-basereverse breakdown voltage of at least 156 volts, and an unusually highemitter-to-collector reverse breakdown voltage of at least 156 volts.This 156 volts is the peak voltage magnitude of a 110 VAC 60 Hz RMSsinusoidal supply voltage that the RBJT integrated circuit may beemployed to rectify. In the case of a PNP-type RBJT integrated circuit,the integrated circuit comprises a P− type epitaxial silicon layer grownon and disposed on a P++ type silicon substrate layer. An N type baseregion extends down into the P− type epitaxial layer from an uppersemiconductor surface of the epitaxial layer, and a plurality of P++type annular collector regions extend down into the N type base regionfrom the upper semiconductor surface. The structure also includes aplurality of N type cathode diffusion regions, each of which extendsdown into the epitaxial layer from the upper semiconductor surface. Eachof the annular P++ type collector regions has a central hole, andsurrounds a corresponding one of the cathode diffusion regions. Certainportions of the P− type epitaxial layer are the emitter of the PNPbipolar transistor of the RBJT device, whereas other portions of the P−type epitaxial layer are the anode of the parallel-connected distributeddiode of the RBJT device. The diode is “distributed” in that its PNjunction is distributed across a large portion of the integrated circuitarea, and is not just locally disposed in one small part of theintegrated circuit. The P type anode of the distributed diode is coupledto the emitter of the PNP bipolar transistor. The N type cathode of thedistributed diode is coupled to the collector of the PNP bipolartransistor. A collector metal electrode is coupled to the collectorregions of the PNP bipolar transistor and to the cathode regions of thedistributed diode, but is not coupled either to any P− type silicon ofthe epitaxial layer or to the base region. A base metal electrode iscoupled to the base of the PNP bipolar transistor, but is not coupled tothe collector of the bipolar transistor, or to the emitter of the PNPbipolar transistor, or to any of the cathode diffusion regions of theparallel-connected distributed diode. The entire bottom surface of theP++ type substrate silicon layer is covered with metal. This metal is anemitter metal electrode of the RBJT integrated circuit.

In one novel aspect, the base region of the RBJT integrated circuit isphysically and electrically separated from the collector metal electrodeby washer-shaped insulation layer features. These washer-shapedinsulation layer features also separate the collector metal electrodefrom P− type silicon of the epitaxial layer where the P− type silicon ofthe epitaxial layer surrounds the cathode diffusion regions. Theresulting isolation and separation of the N type base regions from thecollector metal electrode and from the N type cathode diffusion regionsprevents base current leakage during steady state on operation when theRBJT is to be fully on and conducting current in a rectifyingapplication.

In another novel aspect, a complementary NPN-type RBJT integratedcircuit is disclosed. In similar fashion to the PNP-type RBJT integratedcircuit described above, the complementary NPN-type RBJT integratedcircuit also has washer-shaped insulation layer features that preventbase current leakage through the RBJT during steady state on operation.The layer of epitaxial silicon into which the base region extends is anemitter/distributed diode electrode layer in that it serves both as theemitter of the bipolar transistor as well as one of the diode electrodes(in this case, the P type anode electrode) of the distributed paralleldiode.

In yet another novel aspect, an AC Line Filter/Rectifier Module(ACLF/RM) is disclosed. The novel ACLF/RM performs both AC line filterfunctions as well as a full-wave bridge rectifying function. In oneexample, the ACLF/RM receives a 110 VAC RMS supply voltage onto inputterminals of the ACLF/RM, performs full-wave rectification and linefiltering, and outputs a full-wave rectified version of the input supplyvoltage signal onto output terminals of the ACLF/RM. A full-wave bridgerectifier within the ACLF/RM comprises two of the novel NPN RBJTintegrated circuits and two of the novel PNP RBJT integrated circuits. Atwo-winding inductor of the ACLF/RM provides the proper drive basecurrents to the four RBJT integrated circuits such that the four RBJTintegrated circuits turn on and off as appropriate at the proper timesand operate as a full-wave bridge rectifier.

Further details and embodiments and techniques are described in thedetailed description below. This summary does not purport to define theinvention. The invention is defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, where like numerals indicate like components,illustrate embodiments of the invention.

FIG. 1 is a front view of an AC Line Filter/Rectifier Module (ACLF/RM)in accordance with one novel aspect.

FIG. 2 is a side view of the ACLF/RM of FIG. 1.

FIG. 3 is a bottom view of the ACLF/RM of FIG. 1.

FIG. 4 is a perspective view of the ACLF/RM of FIG. 1.

FIG. 5 is a perspective view from the vantage of a front/bottom cornerof the ACLF/RM of FIG. 1.

FIG. 6 is a perspective view from the same vantage as FIG. 4 except thatthe metal housing of the ACLF/RM is not shown.

FIG. 7 is a circuit diagram that illustrates current flow through theACLF/RM of FIG. 1.

FIG. 8 is a simplified circuit diagram of one of the PNP-type RBJTintegrated circuits of FIG. 7.

FIG. 9 is a top-down view of the RBJT integrated circuit of FIG. 8.

FIG. 10 is a diagram that includes at the bottom a cross-sectional sideview of a rectangle portion of the RBJT integrated circuit of FIG. 9,and also includes at the top a cross-sectional top-down view of the samerectangle portion of the RBJT integrated circuit of FIG. 9.

FIG. 11 is a table that sets forth doping concentrations and depths andother parameters and characteristics and dimensions of the RBJTintegrated circuit of FIG. 9.

FIG. 12 is a cross-sectional diagram that illustrates a PNP-type RBJTintegrated circuit structure as disclosed in U.S. Pat. No. 8,648,399.

FIG. 13 is a cross-sectional diagram that illustrates an operation ofthe novel PNP RBJT integrated circuit 23.

FIG. 14 illustrates current flow through the RBJT integrated circuitdevice of FIG. 12 in a steady-state on condition.

FIG. 15 illustrates current flow through the novel RBJT integratedcircuit device of FIG. 13 in a steady-state on condition.

FIG. 16 is an IV (current-to-voltage) curve for the novel PNP-type RBJTintegrated circuit 23 of FIG. 9.

FIG. 17 is a waveform diagram that illustrates how the novel PNP-typeRBJT integrated circuit 23 of FIG. 9 turns on and then off during afirst half cycle of a sinusoidal 110 VAC 60 Hz supply voltage.

FIG. 18 is a simplified circuit diagram of one of the NPN-type RBJTintegrated circuits of FIG. 7.

FIG. 19 is a cross-sectional diagram of a part of the NPN-type RBJTintegrated circuit of FIG. 18.

DETAILED DESCRIPTION

Reference will now be made in detail to background examples and someembodiments of the invention, examples of which are illustrated in theaccompanying drawings.

FIG. 1 is a front view of one embodiment of an AC Line Filter/RectifierModule (ACLF/RM) 1 that includes a full-wave bridge rectifier, where thefull-wave bridge rectifier involves four efficient RBJT “low forwardvoltage rectifiers” in accordance with one novel aspect. FIG. 2 is aside view of the ACLF/RM 1. FIG. 3 is a bottom view of the ACLF/RM 1.The ACLF/RM 1 performs an AC line filtering function as an ordinary ACline filter does, but the ACLF/RM also performs a full-waverectification function. More particularly, the full-wave bridgerectifier in the ACLF/RM includes two NPN RBJT integrated circuitdevices (that operate as two low forward voltage rectifiers) and two NPNRBJT integrated circuit devices (that operate as two more low forwardvoltage rectifiers). Two two-winding inductors of the ACLF/RM bothperform AC line filtering functions, and also perform a currentsplitting function for driving the RBJT integrated circuits so that theRBJT integrated circuits will operate properly as low forward voltagerectifiers in the full-wave bridge rectifier.

Advantageously, the ACLF/RM 1 of FIG. 1 has the appearance of a commoncommercially available AC line filter module. The ACLF/RM 1 includes anIEC 60320 C14 AC inlet power socket portion 2, a metal housing 3, andthree DC output module terminals 4, 5 and 6. The AC inlet power socketportion 2 includes three AC input module terminals 7, 8 and 9. AC inputmodule terminal 8 is coupled to DC output module terminal 5. Theseterminals 8 and 5 are ground terminals. There are multiple ways ofrealizing the metal housing 3. In one example, two metal pieces arewelded or otherwise joined together to make the metal housing. These twopieces are a stamped scoop-shaped case portion 3A a flat planar coverportion 3B.

FIG. 4 is a perspective view from the vantage of a front/top corner ofthe ACLF/RM 1. FIG. 5 is a perspective view from the vantage of afront/bottom corner of the ACLF/RM 1. Terminal 5 is a tab terminal thatis connected by a rivet to the metal housing 3. Terminal 5 is alsoelectrically connected to terminal 8 via a metal wire or strip. Terminal6 is a tab terminal that is insulated from the metal housing 3 by aninsulative plastic standoff 10 and insulative washer 11 and a secondinsulative washer (not shown) located on the inside of the metalhousing. Electrical connection is made from the metal tab terminal 6 onthe outside of the metal housing, via a rivet through the center of theinsulative standoff 10 and the centers of the washer 11 to a rivet head(not shown) located on the inside of the metal housing. The rivet bothholds the parts 6, 10 and 11 together and also provides electricalcontinuity from the terminal tab 6 on the outside of the metal housingto the rivet head on the inside of the metal housing. Terminal 4 isfixed to the metal housing 3 in similar fashion.

FIG. 6 is a perspective view from the same vantage as FIG. 4 except thatthe metal housing 3 is not shown. The inlet power socket portion 2 has ahardened plastic block portion 2A that fits into and engages the openend of the metal housing 3. The three terminals 7, 8 and 9 are stampedmetal members that extend through the plastic block portion 2A and thenturn downward and engage a printed circuit board 14. Disposed on andsoldered to the printed circuit board 14 are a first capacitor 15, asecond capacitor 16, a third capacitor 17, a first two-winding inductor(transformer) 18, a second two-winding inductor (transformer) 19, afirst packaged novel RBJT integrated circuit device 20, a secondpackaged novel RBJT integrated circuit device 21, a third packaged novelRBJT integrated circuit device 22, a fourth packaged novel RBJTintegrated circuit device 23, and a bleed resistor 24 (not shown). Eachpackaged novel RBJT integrated circuit device includes an integratedcircuit die disposed in a standard three-terminal TO-262 package, wherethe die includes a bipolar transistor and a parallel-connecteddistributed diode. Each packaged RBJT integrated circuit has a reversebreakdown withstand voltage between its emitter and base packageterminals of at least 156 volts, and also has a reverse breakdownwithstand voltage between its collector and base package terminals of atleast 156 volts.

FIG. 7 is a circuit diagram of the circuit of the ACLF/RM 1. A 110 VACRMS 60 Hz supply voltage is present between the “line” input moduleterminal 7 and the “neutral” input module terminal 9. The ACLF/RMreceives this 110 VAC supply voltage on its input terminals, andperforms its full wave rectification function, and outputs the resultingfull wave rectified voltage across its output terminals 6 and 4. As thepolarity of the AC supply voltage between terminals 7 and 9 alternates,current flows through the ACLF/RM circuit in different ways. FIG. 7shows current flow in one direction when there is a positive voltage onthe line terminal 7 with respect to the neutral terminal 9. The arrowsshown in heavy solid lines represent the path of main current flowwhereas the arrows shown in lighter dashed lines represent the basedrive current. The main current path extends from the line terminal 7,through a first winding 25 of the two-winding inductor 19, through theRBJT integrated circuit device 20, and out of the ACLF/RM via outputterminal P 6, and then back into the ACLF/RM via output terminal N 4,through PNP RBJT integrated circuit device 23, through the secondwinding 26 of the two-winding inductor 19, and out of the ACLF/RM viathe neutral input terminal 9. The four RBJT integrated circuits 20-23are coupled together as a full-wave bridge rectifier as shown, with thebase drive currents for the RBJT integrated circuits being supplied bythe current-splitting two-winding inductors 18 and 19. The base currentfor driving the RBJT integrated circuits 20 and 23 flows as shown by thedashed arrows through a first winding 27 of the two-winding inductor 18,and into the base of the NPN RBJT integrated circuit device 20, and outof the out of the ACLF/RM via output terminal P 6, and then back intothe ACLF/RM via output terminal N 4, and out of the base of the PNP RBJTintegrated circuit device 23, through the second winding 28 of thetwo-winding inductor 18, and out of the ACLF/RM via the neutral inputterminal 9.

FIG. 8 is a schematic circuit diagram of the PNP RBJT integrated circuit23 of FIG. 7. The RBJT integrated circuit 23 has a first terminal 29, asecond terminal 30 and a third terminal 31. The RBJT integrated circuitincludes a PNP bipolar transistor 32 and parallel-connected distributeddiode 33. The cathode 34 of the diode is coupled to the collector of thebipolar transistor and to terminal 29. The anode 35 of the diode iscoupled to the emitter of the bipolar transistor and to terminal 31. Thebase of the bipolar transistor is coupled to terminal 30.

FIG. 9 is a top-down diagram of the PNP RBJT integrated circuit 23 ofFIG. 8. The top of the integrated circuit is actually covered withpassivation, with the exception of the base pad area 36 and thecollector pad area 37. The base pad area 36 is actually part of thelarger base metal terminal and electrode 30. Similarly, the collectorpad area 37 is actually a part of the larger collector metal terminaland electrode 29. The emitter metal terminal and electrode 31 (notshown) is disposed on the bottom side of the die.

FIG. 10 is a diagram that includes at the bottom a cross-sectional sideview of the rectangle portion 38 of the RBJT integrated circuit 29 shownin FIG. 9, and also includes at the top a cross-sectional top-down viewof the rectangle portion 38. The cross-sectional side view at the bottomof FIG. 10 is taken along the section line A-A′ in the top view of FIG.10. The cross-sectional top-down view at the top of FIG. 10 is takenalong the sectional line B-B′ in the bottom view of FIG. 10.

A P− type layer 39 of epitaxial silicon is grown on a P++ type layer 40of monocrystalline bulk silicon substrate wafer material. An N type baseregion 41 is formed by ion implantation and subsequent thermal diffusionso that it extends from the upper surface 42 of the epitaxial layer 39and down into the layer 39. Parts of the base region 41, as well aplurality of guard rings 43-45 are implanted and are diffused deeper toform the deeper parts of the N type regions as shown. Moreover, aplurality of still deeper distributed diode diffusion regions (N typecathode diffusion regions) 46-48 are also formed into the layer 39. Notall the cathode diffusion regions are numbered in the diagram, but thecathode diffusion regions are disposed in a two-dimensional array acrossthe surface of the integrated circuit as is seen in the top view of FIG.10.

A plurality of P++ type collector regions 49-52 is formed by ionimplantation and thermal diffusion so that the collector regions extenddown into the base region as shown. Each of these P++ type collectorregions has a somewhat rectangular annular shape when considered fromthe top-down perspective. Each has a circular central hole, and ringsaround and surrounds a corresponding one of the plurality of N typecathode diffusion regions. These deeper N type cathode diffusion regionstogether are the cathode 34 of the parallel-connected distributed diode33. P− type silicon of the epitaxial layer encircles and surrounds theperipheral sides of each N type cathode region so that the N typecathode region does not adjoin and does not merge with any part of the Ntype base region. A layer of insulation is patterned into a plurality ofinsulation features 53-60, including annular insulation features 54-60.The layer of insulation in one example is a 1.0 micron thick layer ofchemical vapor deposition (CVD) deposited silicon oxide. The collectormetal electrode 29 makes contact with the collector regions 49-52. Thecollector metal electrode 29 includes patterned parts of a first metallayer and patterned parts of a second metal layer. The collector metalelectrode 29 also makes contact with each of the plurality of N typecathode regions 46-48 as shown. Importantly, however, the collectormetal electrode 29 does not contact any part of the N type base region41. In addition to the collector metal electrode, the RBJT integratedcircuit also includes the base metal electrode 30. This base metalelectrode 30, like the collector metal electrode 29, includes patternedparts of the first metal layer and patterned part of the second metallayer. The base metal electrode 30 makes contact with the base region 41as shown, but does not make contact with any of the collector regions orany of the cathode regions or with the collector metal electrode.Reference numeral 61 identifies a second insulation layer. The entirebottom surface of the substrate silicon layer 40 is covered with a layerof metal. This metal layer is the emitter metal electrode 31 of theintegrated circuit device. The P-type layer 39 is an emitter/distributeddiode electrode layer, some parts of which are the emitter of thebipolar transistor of the RBJT integrated circuit, and other parts ofwhich are an electrode (in this case, the anode electrode) of thedistributed parallel diode of the RBJT integrated circuit.

FIG. 11 is a table that sets forth doping concentrations and depths andother parameters and characteristics and dimensions of the PNP RBJTintegrated circuit 23.

FIG. 12 is a cross-sectional diagram that illustrates a PNP RBJTintegrated circuit structure as disclosed in U.S. Pat. No. 8,648,399.U.S. Pat. No. 8,648,399 discloses and discusses an application for a lowforward voltage rectifier in the secondary side of a switching flybackconverter. In the flyback converter application, the low forward voltagerectifier is called on to turn on and off at a relatively high switchingfrequency of the main switch of the flyback converter. This switchingfrequency may, for example, be 30 kHz or more. Consequently, the RBJTintegrated circuit should turn on and conduct current, and then turn offrelatively quickly when one of the current pulses has ended. When theRBJT integrated circuit device is fully on and the bipolar transistorportion of the device is on and saturated, the base current I_(B) can beconsidered as having four components: 1) a current due to electronsreaching the P++ substrate and recombining there with holes as indicatedby arrow 62; 2) a current due to electrons reaching the P− epitaxiallayer and recombining there with holes as indicated by arrow 63; 3) acurrent due to electrons passing through the base region and recombiningthere with holes as indicated by arrow 64; and 4) a current due toelectrons passing through the base region and reaching the collectorelectrode and recombining with holes there as indicated by arrow 65. Thedevice of FIG. 12 exhibits a faster turn off than the device of FIG. 13,and it is believed that a reason for this is that the fourth currentindicated by arrow 65 reduces the concentration of charge carriers inthe P− epitaxial layer and thereby promotes faster turn off of thedevice. This faster turn off is generally desirable in a high-frequencyswitching application because the rectifier RBJT is called up to turn onand turn off many times a second, and a slow turn off would result in asubstantial amount of aggregate time when the device is still conductingsome current but is not fully on. In a low frequency 60 Hz switchingapplication, however, it has been found that providing the current pathfrom the base electrode and under the collector region and to thecollector metal electrode as indicated by arrow 65 is undesirable. Ithas been found that during the steady state on condition of the RBJTintegrated circuit, when the bipolar transistor is to be fully on andsaturated, there is a constant steady state leakage of base current outof the collector metal electrode. Due to this leakage of base current, alarger amount of overall base current (from the perspective of outsidethe RBJT integrated circuit) is required in order to achieve a givenemitter current flow through the device. For the bipolar transistor tooperate in saturation under normal I_(C) current levels, the basecurrent must be about one quarter of the collector current. If some ofthe base current flowing through the base metal electrode does notcontribute to this one quarter requirement, but rather is wasted due toleakage to the collector metal electrode, then even more base current isrequired (from the perspective of outside the RBJT integrated circuit)in order to supply the necessary one quarter of I_(C) base current forbipolar transistor saturation. Accordingly, the leakage of base currentpresent in the structure of FIG. 12 reduces efficiency of the RBJTintegrated circuit device in the low frequency 60 Hz rectifierapplication.

FIG. 13 is a cross-sectional diagram that illustrates an operation ofthe novel PNP RBJT integrated circuit 23. The steady state on basecurrent can be thought of as having the same four components asillustrated in FIG. 12, except that in the novel structure of FIG. 13the fourth component of current flow 65 passes laterally out of the baseregion 52, through an amount of P− type silicon, and into the N typecathode region 48, and only then passes upward to the collector metalelectrode 29. The two PN junctions across which this current must flowis thought to reduce the magnitude of the fourth current componentsubstantially as compared to the magnitude of the fourth currentcomponent in the structure of FIG. 12. The intervening patterned feature60 of insulation blocks current flow from passing upward from the N typebase region 41 directly into the collector metal electrode 29, and alsoblocks current flow from passing upward from the P− type epitaxialsilicon (P− silicon between the base region 41 and the cathode region48) directly into the collector metal electrode 29. This insulationfeature 60 has a ring-shape or washer-shape when considered from thetop-down perspective. It covers the circular boundary surface where theN type base region 41 reaches the upper semiconductor surface 42, and italso covers the circular boundary surface where P− type silicon of theemitter/anode layer 39 reaches the upper semiconductor surface 42. Fromthe top-down perspective, these two boundary surfaces appear asconcentric rings, and the ring-shaped insulation feature 60 covers themboth. From the top-down perspective, the ring-shaped insulation feature60 extends around and covers the outer circular periphery of the top ofthe cathode region 48 where the N type material of the cathode region 48reaches the upper semiconductor surface 42. Due to the isolation of thebase region from the collector metal electrode, however, there is littleor no steady state leakage of base current to the collector metalelectrode as there is in the RBJT integrated circuit of FIG. 12. Thisserves to reduce power dissipation of the RBJT device of FIG. 13 in thelow frequency application of the ACLF/RM as compared a situation wherethe RBJT device of FIG. 12 were employed in the low frequencyapplication.

FIG. 14 illustrates current flow through the RBJT integrated circuitdevice of FIG. 12 in a steady-state on condition. For ten amperes ofemitter current, approximately six amperes flows out of the base metalelectrode of the device. Power dissipation due to theemitter-to-collector current is only about 1.2 watts due to the lowV_(CE) forward voltage drop of the device, but the power dissipation dueto the current flowing out of the base metal electrode is relativelylarge at about 3.2 watts. The resulting combined power dissipation isabout 4.4 watts.

FIG. 15 illustrates the current flow through the novel RBJT integratedcircuit device of FIG. 13 in a steady-state on condition. For tenamperes of emitter current, only about two amperes flows out of the basemetal electrode of the device. Power dissipation due to theemitter-to-collector current is about 1.6 watts due to the low forwardvoltage V_(CE) drop of the device, while at the same time the powerdissipation due to the current flowing out of the base metal electrodeis a relatively small 1.6 watts. The resulting combined powerdissipation is about 3.2 watts.

FIG. 16 is an IV (current-to-voltage) curve for the novel PNP RBJTintegrated circuit 23 of FIG. 13. If the RBJT integrated circuit 23 hasa collector current of at least I_(C-CRIT) in the application circuit ofFIG. 7, and if the collector current is not greater than the I_(RATED)value of eight amperes, then the V_(CE) forward voltage drop across theRBJT integrated circuit 23 will be not more than the rated 0.2 volts.

FIG. 17 is a waveform diagram that illustrates how the novel PNP RBJTintegrated circuit 23 turns on and then off during a first half cycle ofa 110 VAC 60 Hz supply voltage. Initially, as the current flowing intothe ACLF/RM increases from zero current at the moment when the absolutevalue of input voltage becomes higher than the output capacitor voltage,the forward voltage V_(CE) across the RBJT integrated circuit increases.The bipolar transistor is initially off and is not conducting current.When the forward voltage V_(CE) across the RBJT integrated circuitexceeds the threshold voltage V_(T) of the parallel diode, which isabout 0.65 volts, then the parallel diode begins to conduct a smallamount of current. As the collector current I_(C) through the RBJTintegrated circuit increases further, the V_(CE) voltage drop across thedevice is limited by the diode. As the current I_(C) through the RBJTintegrated circuit continues to increase, the base current flowingthrough the bipolar transistor also increases, and the bipolartransistor begins to turned on at time t2. As the bipolar transistorturns on, the V_(CE) across the RBJT integrated circuit begins todecrease. As the current though the base of the bipolar transistorincreases still further, the bipolar transistor becomes saturated attime t3. This occurs when the current I_(C) reaches the critical currentI_(C-CRIT). At this point, the forward voltage drop V_(CE) across thedevice has dropped to about 0.1 volts. The bipolar transistor isoperating in its saturation mode. As the voltage of the 110 VAC supplyvoltage continues to increase, this condition persists and the RBJTintegrated circuit continues to operate in the steady-state on conditionwith the bipolar transistor being in saturation. The AC voltage peak ofthe 110 VAC supply voltage is reached and the voltage of the 110 VACthen begins to decrease. As the AC voltage decreases, so too does thecurrent I_(C) flowing through the device. When the current flow dropsbelow I_(C-CRIT), then there is not enough base current flowing throughthe bipolar device to keep it saturated. The bipolar transistor of theRBJT device therefore comes out of saturation, and the forward voltagedrop VCE across the device begins to rise at time t4. When the V_(CE)forward voltage drop across the device is high enough to exceed the 0.65volt threshold voltage of the diode, the diode begins conducting currentand prevents the V_(CE) voltage from increasing further. As the 110 VACsupply voltage decreases still further, all current flow through thedevice stops and the RBJT integrated circuit is off. During the nexthalf cycle of the 110 VAC supply voltage, this PNP RBJT integratedcircuit 23 and the NPN RBJT integrated circuit 20 are off, and the otherPNP RBJT integrated circuit 21 and the other NPN RBJT integrated circuit22 of the full-wave bridge rectifier conduct. Then in the next halfcycle of the 110 VAC supply voltage, the cycle repeats.

FIG. 18 is a schematic circuit diagram of the NPN RBJT integratedcircuit 20 in accordance with another novel aspect. The RBJT integratedcircuit 20 has a first terminal 80, a second terminal 81 and a thirdterminal 82. The RBBJT integrated circuit 20 includes an NPN bipolartransistor 83 and a parallel-connected distributed diode 84.

FIG. 19 is a simplified cross-sectional diagram of the NPN RBJTintegrated circuit 20 of FIG. 18. The NPN RBJT integrated circuit 20 ofFIG. 19 has a nearly identical structure to the structure of the PNPRBJT integrated circuit of FIG. 10, except that the doping types of thevarious semiconductor regions are reversed. For example, the substratesilicon layer 85 is N++ type, and the epitaxial layer 86 is N− type. Thebase region 87, the guard rings 88-90, and the anode diffusion regions91-93 are P type. Annular N++ type collector regions 94-97 are formedinto the base region 87. All these regions are implanted through theupper semiconductor surface 97, so that they extend down from thesemiconductor surface 97 and into epitaxial silicon. The first metalelectrode 80 contacts both the annular collector regions of the bipolartransistor as well as the anode regions of the distributed diode. The N−type epitaxial layer 86 is an emitter/distributed diode electrode layer,a part of which is the emitter of the bipolar transistor 83, and anotherpart of which is the cathode of the distributed parallel diode 84.

Although certain specific embodiments are described above forinstructional purposes, the teachings of this patent document havegeneral applicability and are not limited to the specific embodimentsdescribed above. Accordingly, various modifications, adaptations, andcombinations of various features of the described embodiments can bepracticed without departing from the scope of the invention as set forthin the claims.

What is claimed is:
 1. An integrated circuit comprising: anemitter/distributed diode electrode layer of a semiconductor material ofa first conductivity type; a base region extending into theemitter/distributed diode electrode layer, wherein the base region is ofa second conductivity type opposite the first conductivity type, whereinthe base region has a first depth at its periphery; a plurality ofcollector regions extending into the base region, wherein the pluralityof collector regions are of the first conductivity type; a plurality ofdistributed diode diffusion regions extending into theemitter/distributed diode electrode layer, wherein the plurality ofdistributed diode diffusion regions are of the second conductivity type,wherein the plurality of distributed diode diffusion regions aredisposed in a two-dimensional array across the integrated circuit,wherein each of the distributed diode diffusion regions is separatedfrom the base region by a respective part of the emitter/distributeddiode electrode layer, and wherein each of the distributed diodediffusion regions has a second depth that is greater than the firstdepth of the base region; a first metal electrode that is coupled to theplurality of collector regions and is coupled to the plurality ofdistributed diode diffusion regions, wherein the first metal electrodeis not coupled to the base region; a plurality of insulation features,wherein the first metal electrode is separated from the base region andfrom the emitter/distributed diode electrode layer by the plurality ofinsulation features; a second metal electrode that is coupled to thebase regions; and a third metal electrode that is electrically coupledto the emitter/distributed diode electrode layer.
 2. The integratedcircuit of claim 1, wherein the plurality of distributed diode diffusionregions forms a cathode of a distributed parallel diode, and wherein theemitter/distributed diode electrode layer is an anode of the distributedparallel diode.
 3. The integrated circuit of claim 1, wherein theplurality of distributed diode diffusion regions forms an anode of adistributed parallel diode, and wherein the emitter/distributed diodeelectrode layer is a cathode of the distributed parallel diode.
 4. Theintegrated circuit of claim 1, wherein the third metal electrode iselectrically coupled to the emitter/distributed diode electrode layer byan intervening layer of a semiconductor material of the firstconductivity type, wherein the intervening layer contacts theemitter/distributed diode electrode layer and also contacts the thirdmetal electrode.
 5. The integrated circuit of claim 4, wherein thesemiconductor material of the intervening layer is substrate silicon,and wherein the semiconductor material of the emitter/distributed diodeelectrode layer is epitaxial silicon.
 6. The integrated circuit of claim1, wherein the emitter/distributed diode electrode layer has asubstantially planar upper semiconductor layer surface, wherein theupper semiconductor surface contacts one of the insulation features atan annular boundary, wherein the annular boundary surrounds a circularboundary surface of the substantially planar upper semiconductor layersurface, wherein one of the distributed diode diffusion regions forms asolid circle at the substantially planar upper semiconductor layersurface and extends from the circular boundary surface and into theemitter/distributed diode electrode layer.
 7. The integrated circuit ofclaim 1, wherein the emitter/distributed diode electrode layer is anemitter of a bipolar transistor, wherein the base region is a base ofthe bipolar transistor, wherein the plurality of collector regions are acollector of the bipolar transistor, wherein the bipolar transistor hasan emitter-to-base reverse breakdown voltage of at least 156 volts, andwherein an emitter-to-collector reverse breakdown voltage of at least156 volts.
 8. An integrated circuit comprising: an emitter/distributeddiode electrode layer of a semiconductor material of a firstconductivity type; a base region extending into the emitter/distributeddiode electrode layer, wherein the base region is of a secondconductivity type opposite the first conductivity type; a plurality ofcollector regions extending into the base region, wherein the pluralityof collector regions are of the first conductivity type; a plurality ofdistributed diode diffusion regions extending into theemitter/distributed diode electrode layer, wherein the plurality ofdistributed diode diffusion regions are of the second conductivity type,wherein the plurality of distributed diode diffusion regions aredisposed in a two-dimensional array across the integrated circuit, andwherein each of the distributed diode diffusion regions is separatedfrom the base region by a respective part of the emitter/distributeddiode electrode layer, and wherein each of the collector regions is anannular region that rings around a corresponding one of the distributeddiode diffusion regions; a first metal electrode that is coupled to theplurality of collector regions and is coupled to the plurality ofdistributed diode diffusion regions, wherein the first metal electrodeis not coupled to the base region; a plurality of insulation features,wherein the first metal electrode is separated from the base region bythe plurality of insulation features; a second metal electrode that iscoupled to the base regions; and a third metal electrode that iselectrically coupled to the emitter/distributed diode electrode layer.9. A method comprising: forming a bipolar transistor having a base, acollector, and an emitter, wherein the bipolar transistor is formed suchthat a base region extends into a layer of epitaxial silicon, whereinthe bipolar transistor has an emitter-to-base reverse breakdown voltageof at least 156 volts, wherein the bipolar transistor has anemitter-to-collector reverse breakdown voltage of at least 156 volts;forming a distributed parallel diode having a plurality of diffusionregions, wherein each of the diffusion regions extends into the layer ofepitaxial silicon; forming a first metal electrode that couples to afirst electrode of the bipolar transistor and that also couples to afirst electrode of the distributed parallel diode, wherein the firstelectrode of the bipolar transistor comprises a plurality of annulardiffusion regions, and wherein each annular diffusion region surrounds acorresponding one of the plurality of diffusion regions of thedistributed parallel diode; forming a second metal electrode thatcouples to a second electrode of the bipolar transistor, wherein thesecond electrode of the bipolar transistor is the base of the bipolartransistor; and forming a third metal electrode that couples to a thirdelectrode of the bipolar transistor and that also couples to a secondelectrode of the distributed parallel diode, wherein the base region isseparated from the first metal electrode such that the base region iscontacting neither to the first metal electrode nor to the third metalelectrode.
 10. The method of claim 9, wherein the bipolar transistor isa PNP bipolar transistor, wherein the first metal electrode is acollector electrode, wherein the second metal electrode is a baseelectrode, wherein the third metal electrode is an emitter electrode,wherein the first electrode of the distributed parallel diode is acathode electrode, and wherein the second electrode of the distributedparallel diode is an anode electrode.
 11. The method of claim 9, whereinthe bipolar transistor is an NPN bipolar transistor, wherein the firstmetal electrode is a collector electrode, wherein the second metalelectrode is a base electrode, wherein the third metal electrode is anemitter electrode, wherein the first electrode of the distributedparallel diode is an anode electrode, and wherein the second electrodeof the distributed parallel diode is a cathode electrode.
 12. The methodof claim 9, wherein a part of the layer of epitaxial silicon is thesecond electrode of the distributed parallel diode, and wherein the baseregion is separated from the first metal electrode at least in part by aplurality of insulation features.
 13. The method of claim 12, whereinthe first metal electrode is separated from the layer of epitaxialsilicon by the plurality of insulation features.